1. Field of the Invention
This invention relates to an information processing terminal, a transmission privilege rounding system, a transmission privilege rounding method and transmission privilege acquisition rounding method for rounding a transmission privilege for a plurality of nodes on the same network.
2. Description of the Related Art
The communication control system which is used for a bus type LAN or ring type LAN includes a token passing system. The token passing system is to round a token unidirectionally on a transfer path so that a transmission privilege is sequentially delivered with no collision of data. The delivery of the transmission privilege is carried out using a dedicated token frame.
JP-A-11-234310 discloses a method of designating a delivery destination by adding a token into a transmission data frame. Specifically, the station which has acquired the token determines whether or not there is a data to be transmitted (step S30). If there is the data to be transmitted (Y in step S30), the station makes the processing of the user data containing the token (step S31). If there is not the data to be transmitted (N in step S30), the station makes the transmission processing of a token frame.
In the technique described in the above reference, if there is the user data to be transmitted, the station having acquired the token transmits the token contained in the user data. For this reason, it is not necessary to transmit the token frame separately. However, even when there is no data to be transmitted, the station must transmit the token frame. Further, where the station which is to receive the token disappears owing to failure, the token also disappears. In order to continue the communication thereafter, the processing for regenerating the token is required. Moreover, where a new station is to be added, the existing stations must be modified so that the token can be passed to the new station.
This invention has been accomplished in view of the problems described above.
An object of this invention is to provide an information processing terminal, a transmission privilege rounding system, a transmission privilege rounding method and transmission privilege acquisition rounding program which do not produce frame collision when a transmission privilege is rounded without the exchange of the token frame between prescribed nodes.
Another object of this invention is to provide an information processing terminal, a transmission privilege rounding system, a transmission privilege rounding method and transmission privilege acquisition rounding program in which an increase or decrease in the number of nodes on the same network does not affect existing nodes and the processing of rounding a transmission privilege to provide high reliability and expandibility.